The present invention relates to a shaping device for forming a metal workpiece into a cylindrical shape.
Such shaping devices are generally known for producing a pipe from a cylindrically shaped body. A great difficulty lies in shaping thick-walled sheet metal plates, that is, plates having a thickness of, for example, 35 mm, into a very long cylindrical body having a precise circular cross section. There is another difficulty in that, for long pipes, measures must be taken which prevent the forming rolls, particularly the top roll, from bending. This difficulty cannot be overcome by selecting a top roll that has the largest possible diameter because the diameter of the top roll must be smaller than the inner diameter of the cylindrical shape to be produced. Several machines are known for this purpose, all for specific applications:
There is a known three-roll machine whose rolls are displaceably mounted at both ends in a frame. Since, during the deformation of the workpiece, the rolls bend through and this bending is a function of the length and thickness of the roll as well as of the thickness of the workpiece, the use of such a machine is limited to the production of relatively short hollow cylinders. A significant improvement of such machines can be realized by extending the rolls considerably beyond their supports and by exerting a counter-force on the ends of the rolls.
Also known is the use of a folding press with which it is possible to produce long cylindrical shapes. Its drawback is not only that the workpieces worked by a folding press do not have a round but rather a polygonal shape, which has drawbacks under heavy stresses on the pipe, but also that the process operates rather slowly.
Additionally, a pipe press is known which includes a plurality of C-shaped frames to which pressing tools are attached. Although it is possible to produce cylindrical bodies with such machines, that is, polygons having rounded edges, of generally any desired length, a different set of press molds is required for each desired cylinder diameter and for each thickness of sheet metal to be processed, so that the machine is expensive and working with it is time consuming due to the relatively long changeover times involved.
Also known is a press including two die plates which together define a cylindrical cavity. With such a press, a plate can be shaped into a cylindrical hollow body. The drawbacks of this machine are that the production of the press mold is very expensive and is subjected to a considerable amount of wear, tool changes are labor intensive, and the deformation of the workpiece occurs in a considerably forced manner which adversely affects its structure and which results in hardened portions in the region of the seam edges.
There is a known press including two bottom rolls and upper pressing tools. This press is an expensive structure which operates only relatively slowly and, moreover, has a high power consumption, with additional tools being needed to bend the seam ends.
For the production of relatively thin-walled but very long pipes having a small to average diameter, that is, up to about 50 cm, profiling lines are known which include a plurality of paired rollers. These known machines also require special tools for each pipe dimension; tools that are quite expensive and their exchange is time consuming to a great extent.
Other prior art devices exist with which a band-shaped workpiece is wound in the manner of a helix to produce a tubular body. These machines are also not suitable for processing thick-walled workpieces and involve substantial time for changes to accommodate other pipe dimensions.